A polymer electrolyte fuel cell (PEFC) is a fuel cell having a type of interposing a solid polymer electrolyte between an anode and a cathode, and supplying fuel to the anode and oxygen or air to the cathode on which oxygen is reduced, thereby producing electricity. Hydrogen, methanol or the like is mainly used for the fuel. In order to increase a reaction rate in the fuel cell and to enhance energy conversion efficiency thereof, a layer including a catalyst has been so far arranged on a cathode surface and/or an anode surface of the fuel cell. As the catalyst, a noble metal has been generally used, and among the noble metals, platinum having high activity and high stability toward high potential is mainly used. As a support for supporting such a catalyst metal, carbon black has been so far used.
Incidentally, the cathode is temporarily exposed to high potential, for example, about 1.5 V during operation of repeating start and stop of the PEFC. Under such high potential, the carbon support is known to be oxidized and corroded to cause decomposition and degradation in the presence of water. Power generation performance of PEFC decreases by degradation of the support. Further, agglomeration of the noble metal is promoted by degradation of the support and the power generation performance further decreases. Therefore, desire has been expressed for a support or a catalyst having resistance to high potential associated with start and stop, and an electrode catalyst for a fuel cell using the same.
Patent Literature 1 describes a support for supporting a catalyst as obtained by carbonizing a raw material containing a nitrogen-containing organic matter and a metal. Patent Literature 2 describes an electrode catalyst for a fuel cell as produced by a production method, comprising Step 1 for mixing a transition metal-containing compound, a nitrogen-containing organic compound and a solvent to give a catalyst precursor solution, Step 2 for removing the solvent from the catalyst precursor solution, and Step 3 for heat-treating a solid residue at a temperature of 500 to 1,100° C. to give the electrode catalyst, wherein the transition metal-containing compound partially or wholly contains a transition metal element M1 selected from Group 4 elements and Group 5 elements of Periodic Table as a transition metal element. Patent Literature 3 describes a catalyst produced by a production method, comprising a step for allowing a gas of a compound containing a metal element M selected from the group consisting of titanium, iron, niobium, zirconium and tantalum, a hydrocarbon gas, a nitrogen compound gas and an oxygen compound gas to react therewith at 600 to 1,600° C. Patent Literature 4 describes a support for a catalyst, comprising metal oxycarbonitride containing niobium or the like as a metal.
However, any one of the supports or the catalysts described above has had no sufficient resistance to high potential associated with start and stop.